Analysis of variable methylation in the transitional-CpG sites. (A and B) The reproducibility of the 5-level classification with 20%-methylation increment (A) and 10-level classifications with 10%-methylation increment (B) was verified by the proportion of the paired tissue samples showing no differences in the level of methylation. The duplicated DNAs of the same tissue (closed bars), a pair of 1-cm-adjacent tissues (grey bars) and a pair of antrum and body tissues (open bars) were compared. (C and D) Analysis of an intermediate methylation level. The frequency of undermethylated and overmethylated cases was estimated based on an intermediate level spanning two levels (20% methylation) (C) and one level (10% methylation) (D) of 10-level classification common in H. pylori-negative gastric mucosa.